NPR congressional correspondent Andrea Seabrook and I have watched this fall, as outside money groups, unattached to any party or candidate, ranged across the landscape of the midterm elections, firing off attack ads as they went. Now we're starting to see just how wide a swath they cut.

And the Wesleyan Media Project, a three-college consortium analyzing political ads on TV, says the outside groups are running far more attack ads than candidates or party committees, making 2010 the most negative campaign in at least a decade.

And second, the Supreme Court's Citizens United ruling, last January, has made it much easier for corporations and unions to spend money in campaign politics.

The result: While Democrats fortified themselves through aggressive fundraising over the past two years, pro-Republican outside money groups gained a powerful edge of their own, raising money from big donors — and apparently from corporations — while keeping those money sources secret.

The breakdown, according to FEC data tallied by the Sunlight Foundation: $119.2 million in spending for Republicans; $74 million for Democrats, whose donors have stirred recently, but not enough to even things out.

When I counted up the ads by congressional district, I found 90 races where pro-Republican groups were on the air, compared to 27 for pro-Democratic groups.

One example of the disclosure problem, which Andrea and I explored: The Commission on Hope, Growth and Opportunity, which targeted against 11 Democratic House members as of last week. It's organized as a 501(c) (4) "social welfare" group under the tax code, not as a political committee, so it doesn't have to file regular reports with the Federal Election Commission.

But it also files no reports on "electioneering communications" — i.e., ads that run within 60 days of an election and mention a specific candidate. (Most of the "non-political" groups on both sides file those reports, but they leave the donation section blank; the Federal Election Commission created that loophole.)

And like other political advertisers on TV, CHGO must file public reports at stations where it places ads, disclosing how much it paid, when the ads are running, and which candidates it names. When we checked at stations in Pittsburgh last month, we found that CHGO filings gave only a dollar amount — no broadcast schedule, no candidate names.

Now that the election is here, CHGO and the other 501(c)4 groups on both sides will have to navigate a careful legal path. The IRS says their primary purpose cannot be political. They'll need something to balance out all those attack ads, and the solution likely will include more TV ads.

The American Action Network has already started such an ad campaign, urging viewers to tell their House members "to repeal the health care bill this November." The cookie-cutter ad targets vulnerable Democratic incumbents, so it's like a campaign ad and an issue ad — it's two ads in one.